The invention relates to a dual clutch for a transmission with a first transmission input shaft and a second transmission input shaft that is positioned in coaxial relation to the first transmission input shaft.
Such a dual clutch is for instance known from the European patent EP 1 195 537 B1. The dual clutch comprises the coupling flange that can be connected to an engine or motor in a torque transmitting manner. Further, this dual clutch comprises a first clutch and second clutch. Both clutches can be actuated hydraulically. In case of the first clutch, assuming for instance, the closed position torque can be transmitted from the coupling flange to the first transmission input shaft. Accordingly, the second clutch is provided for transmitting torque from the coupling flange to the second transmission input shaft.
Each one of the two clutches comprises several outer clutch discs and several inner clutch discs. Via the clutch comprising an inner clutch discs carrier and via a rotatable clutch housing with a clutch cover the respective inner clutch discs of the first and second clutches are connected in a torque transmitting manner with the coupling flange, respectively. The outer clutch discs of the first clutch are connected to the first transmission input shaft in a torque transmitting manner via the first clutch cap, while the outer clutch discs of the second clutch are connected to the second transmission input shaft in a torque transmitting manner via the second clutch cap.
The clutch hub comprises, apart from the inner clutch discs, also a first hydraulic unit for actuating the first clutch and a second hydraulic unit for actuating the second clutch. The first hydraulic unit can exert pressure in axial direction against the intermittently and adjacent to each other positioned inner clutch discs and outer clutch discs, thereby pressing the inner clutch discs and the outer clutch discs in axial direction against each other. Due to the friction between the clutch discs the first clutch can transmit a torque generated by friction. In an identical manner the second hydraulic unit can actuate the second clutch for transmitting, in its closed position, torque from the clutch hub to the second transmission input shaft.
The clutch hub is supported in a rotatable manner on a clutch axle that is positioned in the coaxial relation to the first transmission input shaft and the second transmission input shaft. The clutch axle not only provides support in a rotatable manner for the clutch hub but also feeds the clutch hub with oil. The first and second hydraulic units require pressurized hydraulic oil for pressing the clutch disc stack together. In addition, by means of the clutch axle, the first and second clutches are fed with cooling oil for conducting off heat resulting from an operational slipping mode of the first and second clutches.
The rotatable clutch housing, together with the clutch cover, forms the closed clutch cup accommodating the first and second clutch as well as the respective clutch caps. Due to the almost entire enclosure by means of the coupling housing that is rotating together with the coupling flange and the motor, no connection between an auxiliary motor provided at the outer circumference of the clutch housing and the first and second clutch caps can be established. To the contrary, it is only possible to connect the auxiliary motor positioned radially outside with the rotatable clutch housing. The connection to the output side of the first or second clutch, that is with the first or second clutch caps, is almost impossible to establish.
It may be possible to connect a rotor of, an electromotor in a torque transmitting manner to the first or outer clutch cap, wherein the rotor is provided within the clutch housing. This means that the stator and rotor would be separated by the wall of the clutch housing from each other. When choosing the right material for the clutch housing and an appropriate radial distance between the rotor and the stator, the desired torque of the electromotor could be transmitted to the first clutch cap and therefore to the first transmission input shaft. However, this results in a relatively complex design of the electromotor.